OEDIPE, a software for personalized Monte Carlo dosimetry and treatment planning optimization in nuclear medicine Absorbed dose and biologically effective dose considerations

International audienceFor targeted radionuclide therapies, treatment planning usually consists of the administration of standard activities without accounting for the patient-specific activity distribution, pharmacokinetics and dosimetry to organs at risk. The OEDIPE software is a user-friendly interface which has an automation level suitable for performing personalized Monte Carlo 3D dosimetry for diagnostic and therapeutic radionuclide administrations. Mean absorbed doses to regions of interest (ROIs), isodose curves superimposed on a personalized anatomical model of the patient and dose-volume histograms can be extracted from the absorbed dose 3D distribution. Moreover, to account for the differences in radiosensitivity between tumoral and healthy tissues, additional functionalities have been implemented to calculate the 3D distribution of the biologically effective dose (BED), mean BEDs to ROIs, isoBED curves and BED-volume histograms along with the Equivalent Uniform Biologically Effective Dose (EUD) to ROIs. Finally, optimization tools are available for treatment planning optimization using either the absorbed dose or BED distributions. These tools enable one to calculate the maximal injectable activity which meets tolerance criteria to organs at risk for a chosen fractionation protocol. This paper describes the functionalities available in the latest version of the OEDIPE software to perform personalized Monte Carlo dosimetry and treatment planning optimization in targeted radionuclide therapies. © 2014 EDP Sciences

Liver Selective Internal Radiation Therapy with 90Y resin microspheres Comparison between pre-treatment activity calculation methods

International audienceDifferent methods to calculate 90Y resin microspheres activity for Selective Internal Radiation Therapy (SIRT) were compared. Such comparison is not yet available and is needed in clinical practice to optimize patient specific treatment planning.32 99mTc-macroagregates (MAA) evaluations were performed, followed by 26 treatments. Four methods to calculate 90Y-activity were applied retrospectively three based on Body Surface Area and one based on MIRD formalism, partition model (PM). Relationships between calculated activities, lung breakthrough (LB), the activity concentration ratio between lesions and healthy liver (T/N) and tumour involvement were investigated, where lobar and whole liver treatments were analysed separately.Without attenuation correction, overestimation of LB was 65%. In any case, the estimated lungs' doses remained below 30Gy. Thus, the maximal injectable activity (MIA) is not limited by lungs' irradiation. Moreover, LB was not significantly related to T/N, neither to tumour involvement nor radiochemical purity (RP).Differences in calculated activity with the four methods were extremely large, in particular they were greater between BSA-based and PM activities for lobar treatments (from-85% to 417%) compared to whole liver treatments (from-49% to 61%). Two values of T/N ratio were identified as thresholds for BSA-based methods, healthy liver doses are much higher than 30Gy when T/Nandlt;3; for PM, tumour doses are higher than 120Gy when T/N andgt; 4. As PM accounts for uptake ratio between normal and tumour liver, this method should be employed over BSA-based methods. © 2014 Associazione Italiana di Fisica Medica